Jack

You mention a lot of things, so not sure what you mean by 'this sort of thing' but maybe that's just me.

As Scott wasn't English, Roud doesn't cover him. But he does complain about collectors who re-write stuff, giving Percy of Reliques fame as an example, saying it his work is mostly useless as a result.

But Roud does not attempt a 'literary' analysis of the sort Evelyn Kendrick Wells appears to have provided.

I'm not sure we actually know much about written medieval songs.

Roud provides various contemporary accounts of how/what people did sing together through the centuries covered in detail in his book, but I don't recall him mentioning introductory patter. His sources are autobiographies and so on. These sources suggest that the ordinary people often sang 'commercial' materials, which for some means it cannot count as 'folk', but irrespective of definitions, I think it is an interesting aspect of popular culture and one worth noting.

Roud does acknowledge change through time. He collects and indexes different versions of songs, and their sources. I think he asserts that once print happens, you won't get a 'pure' oral tradition, another idea which is controversial. I think Jim Carroll would perhaps argue that 'folk' singers knew which songs were 'in the tradition' and which were not. Roud thinks that written and oral intertwine over time.

Hope I haven't misrepresented this.